One of the things I love about Sencha Touch is the built in themes. Android has 4.x has two themes: Halo Dark, Halo Light. There is only one Android theme for Sencha Touch and it's dark. I've been bugging them for awhile to include a light theme and their response was "You do it".
I googled for a long time and couldn't find a theme someone else did. I gave in and decided to make my own theme after finding this one. It's beautiful. I read his breakdown and he created a theme by copying the winPho theme and made changes until he was happy. I did something similar. I copied the Android theme and started digging in.
That's when I found it. There is a Sass variable in /[Sencha SDK folder]/resources/themes/stylesheets/sencha-touch/mountainview/var/_Class.scss called $dark-theme. If you set this variable to false in your local sass file for android it becomes a light theme.
I wish this was explained better. It's only through source code diving can we find the true answers.